Orbit Racers is an oldie but a goodie -- it's basically a very simplistic racing game, but the twist is that there is only one button in the game, the space bar. The entire game is controlled with that one button.

How does that work? Letting go of the space bar moves you toward the center of the track, and pushing it moves you away. Because you don’t want to hit either side of the track, you will continuously tap the space bar throughout the races, avoiding obstacles and targeting speed boost arrows.

Every race is a perfect circle, orbiting some center of gravity. After you get used to the controls it’s rather simple and gets tedious (there are 10 laps for each track, and the tracks are all circles so they don’t vary very much), but the idea of a single-button game alone made it worth playing.